What difference does having a single end or double end make?

[clownfool]

I have a aquapod 24g with HQI 150w metal halide bulb.
What is HQI mean?
What difference does having a single end or double end make?
Is the DE use less power?
Put off less heat?
Better for my SPS?

 

[Len]

Hi. HQI is now a term used synonymously with double-ended (although it's true meaning, Halogen Quartz Iodide, is actually a very specific technology). Basically, anytime you hear a hobbyist say HQI, he/she is just talking about double ended bulbs.

DEs don't really have an advantage over single ended except they are more compact. Hobbyist used to believe DE were more efficient, but PPFD tests published in www.advancedaquarist.com do not support this myth. Bottom line is, go DE or SE, whichever best fits your system.

 

[Unarce]

I'm in agreement with Len's assessment. To go even further, there are advantages and disadvantages for either one.

Double-end bulbs are shorter and thinner, making them more conducive for use in small areas. Similar to the effect of T5's, the DE bulb's build, allows a well designed reflector to reflect more light downwards with less restrke. This is one reason why many believed DE's threw out more PAR per watt. That's probably better explained with how DE reflectors focus more of the light downwards in a tighter area. In comparison, single-end bulbs have a greater spread of light. SE bulbs are also already equipped with a glass envelope that blocks out harmful UV-A and UV-B rays. DE bulbs do not have this, which is why a pendant with a glass shield is a must (which will cut off up to 15% of the PAR value).

Hobbyists also find it easier to DIY retro kits for SE bulbs, as placing the fittings for DE's is tricky.